TELEREADER CWR-685E, Service Manual

Page: 7 / 40

7
2.3 Control of SW OUT REMOTE
The SW OUT REMOTE terminal of the rear panel is connected to the REMOTE (J3-4) terminal of
main PCB.
This terminal is directly shorted by the contact of the SEND-AUTO-RECEIVE switch when this
switch is set to SEND side. When AUTO or RECEIVE position is selected, this terminal is controlled
by the TR9 on the main PCB.
This terminal and the SEND-AUTO-RECEIVE switch is so wired that the J8-5 on the main PCB may
be connected to GND when the switch is set to SEND position, and that the J8-8 is similarly con-
nected to GND when it is set to RECEIVE side. Thus, this terminal always monitors the state of this
switch, and controls the transmission and reception and TR9.
2.4 Flow of signal in transmission
When a key is depressed, an ASCII code of 8-bit parallel positive logic is delivered from the key-
board, and is given from pin 4 to pin 11 of J6 on the main PCB. In succession, a data strobe signal
of negative logic is applied to pin 13 of J6, and is converted to a pulse signal by the one-shot mul-
tivibrator in IC6 to be fed in pin 40 of IC32.
At this time, according to the initially set format, the IC32 set the IRQB (pin 37) to L level in order
to ask the MPU to read data. In consequence, the MPU, immediately or after finishing the process
being run at that time, reads the data from the keyboard being applied to PA0 to PA7 in IC32, and
returns the IRQB to H level at the same time, and delivers a data reading acknowledgement signal
to the CA2 (pin 39) as negative logic pulse signal of 1.183 µs. The ACK signal is not used when
feeding from the keyboard, but is used when controlling the system by means of other microcom-
puter or the like instead of the keyboard. In such a case, the parallel data should not be converted
until the response of ACK signal is confirmed.
When the MPU reads the data, a process suited to the state, such as command processing, writing
into transmission buffer area, writing into memory area, is effected according to the data.
REFERENCE
o In transmission of CW, the data in the transmission buffer is converted to CW code, and the
output of CW output port (pin 2 of IC27) is controlled being synchronized with the clock
signal created in IC35 and read in from pin 2 of IC40. This clock frequency may be varied
by means of SPEED slide VR in the front panel.
When the CW output port becomes H level at TTL level, the TR5 and TR8 are turned on, so
that a key operation signal can be obtained from the SW OUT CW output terminal in the re-
ar panel connected to J3-6. In CW ID mode at the time of RTTY, the TR10 is turned off by
the signal of CW ID output port (pin 9 of IC27) which is operating simultaneously with CW
output port, and the signal is shifted to a blank space.
o In transmission of RTTY, when the MPU writes data into USART, they are converted to serial
signals in synchronism with the baud rate at 1/16 of the clock given to pin 9 of USART
(IC28), and are delivered from TXD (pin 19) of USART, thereby controlling the TTL-OUT
(J10-3 terminal) and TR10 as in the case of CW ID. The TTL-OUT (J10-3 terminal) of main
PCB is connected to the FSK (J6-2 terminal) on MODEM PCB, and is delivered at TTL level
to the FSK TTL OUT terminal in the rear panel from the FSK TTL (J4-9 terminal). The FSK
signal is, at the same time, applied also to pin 5 of IC4 as AFSK shift signal. The AFSK sig-
nal created here is delivered from J4-3 terminal on MODEM PCS, and is sent to the AFSK